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/* This is a module which is used for setting the TOS field of a packet. */
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <net/checksum.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ipt_TOS.h>
static unsigned int
target(struct sk_buff **pskb,
unsigned int hooknum,
const struct net_device *in,
const struct net_device *out,
const void *targinfo,
void *userinfo)
{
struct iphdr *iph = (*pskb)->nh.iph;
const struct ipt_tos_target_info *tosinfo = targinfo;
if ((iph->tos & IPTOS_TOS_MASK) != tosinfo->tos) {
u_int16_t diffs[2];
/* raw socket (tcpdump) may have clone of incoming
skb: don't disturb it --RR */
if (skb_cloned(*pskb) && !(*pskb)->sk) {
struct sk_buff *nskb = skb_copy(*pskb, GFP_ATOMIC);
if (!nskb)
return NF_DROP;
kfree_skb(*pskb);
*pskb = nskb;
iph = (*pskb)->nh.iph;
}
diffs[0] = htons(iph->tos) ^ 0xFFFF;
iph->tos = (iph->tos & IPTOS_PREC_MASK) | tosinfo->tos;
diffs[1] = htons(iph->tos);
iph->check = csum_fold(csum_partial((char *)diffs,
sizeof(diffs),
iph->check^0xFFFF));
(*pskb)->nfcache |= NFC_ALTERED;
}
return IPT_CONTINUE;
}
static int
checkentry(const char *tablename,
const struct ipt_entry *e,
void *targinfo,
unsigned int targinfosize,
unsigned int hook_mask)
{
const u_int8_t tos = ((struct ipt_tos_target_info *)targinfo)->tos;
if (targinfosize != IPT_ALIGN(sizeof(struct ipt_tos_target_info))) {
printk(KERN_WARNING "TOS: targinfosize %u != %Zu\n",
targinfosize,
IPT_ALIGN(sizeof(struct ipt_tos_target_info)));
return 0;
}
if (strcmp(tablename, "mangle") != 0) {
printk(KERN_WARNING "TOS: can only be called from \"mangle\" table, not \"%s\"\n", tablename);
return 0;
}
if (tos != IPTOS_LOWDELAY
&& tos != IPTOS_THROUGHPUT
&& tos != IPTOS_RELIABILITY
&& tos != IPTOS_MINCOST
&& tos != IPTOS_NORMALSVC) {
printk(KERN_WARNING "TOS: bad tos value %#x\n", tos);
return 0;
}
return 1;
}
static struct ipt_target ipt_tos_reg
= { { NULL, NULL }, "TOS", target, checkentry, NULL, THIS_MODULE };
static int __init init(void)
{
if (ipt_register_target(&ipt_tos_reg))
return -EINVAL;
return 0;
}
static void __exit fini(void)
{
ipt_unregister_target(&ipt_tos_reg);
}
module_init(init);
module_exit(fini);
MODULE_LICENSE("GPL");
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